Cylinder mould for manufacturing fibre cement products

ABSTRACT

APPARATUS FOR MANUFACTURING FIBRE-CEMENT PRODUCTS, WHEREIN A TANK ROTATABLY SUPPORTS A REVOLVING SCREEN IN THE UPPER PORTION THEREOF. THE BOTTOM OF THE TANK INCLUDES TWO SPACED CONVEX PORTIONS INTERCONNECTED BY A CONCAVE PORTION, RELATIVE TO THE TANK INTERIOR, WHICH DEFINE A SMOOTH UNDULATED CONTOUR SURFACE, MIXING PADDLES BEING MOUNTED IN THE CONVEX PORTIONS OF THE TANK. THE SCREEN IS VERTICALLY SPACED ABOVE THE CONCAVE PORTION BY AN AMOUNT SUBSTANTIALLY EQUAL TO 0.1 TO 0.2 TIMES THE OUTER DIAMETER OF THE SCREEN.   D R A W I N G

March 30, 1971 M. s. NEIFELD ETAL 3,573,163

CYLINDER MOULD FOR MANUFACTURING FIBRE-CEMENT PRODUCTS Filed Dec. 70' 196'? United States Patent US. Cl. 162--323 3 Claims ABSTRACT OF THE DISCLOSURE Apparatus for manufacturing fibre-cement products, wherein a tank rotatably supports a revolving screen in the upper portion thereof. The bottom of the tank includes two spaced convex portions interconnected by a concave portion, relative to the tank interior, which define a smooth undulated contour surface, mixing paddles being mounted in the convex portions of the tank. The screen is vertically spaced above the concave portion by an amount substantially equal to 0.1 to 0.2 times the outer diameter of the screen.

The present invention relates to cylinder sheet and pipe moulding machines for manufacturing fibre-cement products, and more particularly to improvements in the design of a tank of the revolving screen type.

One of the determining factors of quality and efficiency in the practice of moulding products of fibre-cement suspension with the use of cylinder mould machines is the hydraulic conditions of the tank operation.

For the purpose of providing the best hydraulic conditions, different designs of tanks have been proposed. Known in the art is a tank with forced circulation of a suspension, subdivided in its bottom part by a partition into two independent zones connected with external pipes to close the circulation.

Said tanks, however, do not ensure ideal hydraulic conditions.

Forced longitudinal circulation of the suspension along the revolving screen axis, as localized in independent zones in the lower part of the tank due to improper mixing in the upper layers, does not ensure uniform dispersion of the suspension and is conducive to segregation, coagulation and thickening thereof, which ultimately results in the sticking of fibre-cement to the inner tank surface and consequently to the necessity of frequent and long-lasting shut-downs of the machine for the purpose of cleaning.

Driving a suspension along the revolving screen axis usually does not provide the necessary conditions which prevent coarse fibre-cement fractions from settling onto the tank bottom and is inadequate to provide a uniform mixing of coarse fractions with fine fractions.

Subdivision of the tank bottom portion into independent zones to provide circulation along the revolving screen axis involves minimizing the space between the revolving screen and tank bottom bulge, which detrimentally affects hydraulic conditions, results in low quality of the layer being filtered within the space zone, and has a noticeable negative elfect upon the product quality.

Because the bulge is located too close to the revolving screen, the peripheral speed of the latter has to be limited, which significantly restricts the machine efficiency.

Accordingly, the principal object of the invention is to eliminate the above disadvantages and provide the best hydraulic conditions for the tank operation for the pur- 'ice pose of obtaining the proper layer on the revolving screen of the moulding machine.

Another object of the invention is to provide conditions for the forced operation of the revolving screen at faster speeds, i.e. to increase significantly the efiiciency of the machine, while retaining at the same time stable quality characteristics of the filtered layer.

These objects are achieved because the tank bottom is smoothly bent as a curvilinear surface forming a concave middle portion facing the revolving screen. Between the top of the concave middle portion and revolving screen there is provided a space of 0.1 to 0.2 of the outer screen diameter. Mixers are thereby mounted in the deepened portions of the bottom and, are located on each of the sides of the concave middle portion. The curvilinear surfaces are cylindrical in part, having axes being approximately coincident with those of the mixers. It is expedient to direct the lateral walls of the tank in its lower part along inclined planes disposed at a tangent to cylindrical surfaces of the bottom.

The present invention will become more fully apparent from the following detailed description of one embodiment thereof when considered in conjunction with the accompanying drawing, the sole figure of which represents a crosswise section of the tank according to the invention.

A tank l1 supporting a revolving screen 2 in its upper portion includes a bottom portion smoothly bent as a curvilinear surface having a concave middle portion 3 arranged in parallel with the axis of rotation of the revolving screen 2,. There is provided a space of 0.1 to 0.2 of the outer screen diameter between the top of the concave middle portion and the revolving screen 2.

The concave middle portion 3 is made semicircular and subdivides the bottom part of the tank 1 into zones 5 and 6 communicating through the space 4 and located in the convex bottom portions 7 and 8 bent as cylindrical surfaces in which horizontal paddle mixers 9 and 10 are mounted such that the axes of cylindrical surfaces approximately coincide with the axes of rotation of mixers. The lateral walls 11 and 12 are inclined in the bottom part, tangentially with respect to convex surfaces 7 and 8 of the bottom.

When in operation, the interaction between the paddle mixers 9 and 10 and revolving screen 2 causes ascending and descending currents in the suspension at the walls of the tank 1, thus preventing segregation of the suspension, its coagulation and settling of coarse fractions and ensuring a uniform mixing of the suspension.

Mixers 9 and 10, while rotating, also agitate current in the suspension at the tank bottom, preventing the suspension from settling either under the paddles or onto the concave middle portion and the lateral walls. Because of the proximity of the revolving screen, the material does not settle down onto the top of the concave middle portion. Thus are provided necessary hydraulic conditions for the tank operation.

What is claimed is:

1. Apparatus for manufacturing fiber-cement products comprising a tank including an upper portion and a lower portion, a cylindrical screen having a central axis of rotation and an outer screen diameter, said screen being rotatably supported in said upper portion of said tank, said lower portion including two spaced lowermost convex portions relative to the tank interior and a concave portion relative to the tank interior interposed between said convex portions and facing the cylindrical screen to define therewith a smooth undulated external contour, said screen being vertically spaced above said concave portion by an amount substantially equal to 0.1 to 0.2 times said outer screen diameter in a vertical plane passing through said axis of rotation, and mixing means in each of said convex portions for mixing fiber-cement provided in said tank.

2. Apparatus as claimed in claim 1, wherein said convex portions are each partially cylindrical having centers of curvature and a longitudinal axis containing the centers of curvature, said mixing means including paddle mixers mounted for rotation substantially about each said longitudinal axis.

3'. Apparatus as claimed in claim 2, wherein said lower portion includes two outermost spaced lateral Walls, inclined relative to one another, each being tangentially connected to a respective one of said convex portions and extending generally vertically and connected with the upper portion of the tank.

References Cited UNITED STATES PATENTS 3,190,792 6/1965 Beachler et a1 l62327X 3,368,936 2/1968 De Long 162334X S. LEON BASHORE, Primary Examiner 10 A. DANDREA, JR., Assistant Examiner U.S. Cl. X.R. 162387 

